Hard dependency to Input System

## Steps to reproduce

Import the `AltTester` unitypackage in a project that doesn't have the `Input System` package installed

## Actual result

### AR

- There is a hard dependency to `Input System` even if one doesn't want to have it in the project when importing the `AltTester` unitypackage in the project.
- There is a compile error in the unity console:` Assets\AltTester\AltServer\AltMockUpPointerInputModule.cs(5,19): error CS0234: The type or namespace name 'InputSystem' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)`

### Additional info

Environment
- tested with _AltTester_ unitypackage `v 1.8.2`

Screenshot with the error in console

## Expected result

### ER

- One should not be forced to install the Input System package after importing the `AltTester` unitypackage when not planning to use it.
- There should be no compile errors in the console

### Additional info

## Testability

Import the `AltTester` unitypackage in an empty new project